Control system



4May 2s, 1946.

M. G. sATEREN E-ArAL CONTROL` SYSTEM Filed April "7,

INVENTORS Marfmeeren and e. fn

ATToRN f Patented May 28, 1946 OFFICE CONTROL SYSTEM Martin G. Sateren, Sharon,

Pa., assi Electric Corporation, corporation of Pennsy and Willard A. VDerrf,

gnors to Westinghouse East Pittsburgh, Pa., a lvania Application April 7; 1945, Serial No. 587,182 4 (Cl. 17g-'2)' 7 Claims.

Our invention relates, generally, to control systems and has reference in particular to supervisory control systems.

Generally stated, it is an object of our inven.

tion to provide a supervisory control system which is simple and inexpensive to manufacture and is reliable in operation.

More specically, it is an object of our invention to provide two-Way supervision cfa.l telephone line which is usedL as a signalling channel in a supervisory control system.

It is alsol an object of our invention to provide for using two different. audio frequencies for sending coded impulse signals from opposite ends of a signalling channel for controlling the operation of apparatus ata remote stationr and for using the same frequencies forl supervising the channel to indicate at. both ends' thereof when there is a short circuit, an open circuit or abnormal attenuation of. the signal.

Another object of our invention is to provide for operating the line relays in a supervisory con trol system on signal voltages ofV dilferent frequencies, and for synchronizing the line relays at both ends. of the system by deenergizing theA am-` pliers operating the line relays each time their associated impulse sending relays operate.

Yet another object of our invention is to provide for normally energizing the line relays at both ends of a supervisory control channel through receivers which are responsive only to diilferent audio-frequency tones and for effecting synchronization of the equipment at both stations during signalling by turning 01T the oscillator at the end which is sending and deenergizing the receiver at that end at the same time. Still another object of our invention is to provide for operating the line relays at the ends of a. signalling channel on signal voltages of differl 4-0 y fault condition on the channel when the signal voltage fromI one endlV ent frequencies which are thereto, andfor indicating a y normally applied becomes too greatly attenuated at the other end or is not received at all for a time interval greater than is normally encountered in. impulse signal ling.

in part be explained hereinafter.

may be read iny connection ing drawing inwhich the embodying the` invention in one of its forms.`

Other objects will in part be obvious, and will` Referring to the drawing, the reference numera] Iii may denote generally a telephone line connecting telephone equipment at a control sta-` tion; with telephone equipment at a remote station adjacent the apparatus which is to be controlled. The telephone equipment may be of any suitable typev comprising, for example, micros` phones II and I2 and telephone receivers I 3 and M at the control and remote stations,` respectively, which may be connected to the telephone line through associated hybrid coils I5 and I6 having articial lines Il and lli, and transformers I9 and 20,7respectivezly. The receivers I3 and I4- may be connected yto their respectitve` hybrid coils through suitable' amplii-ersl 2,2.` and 23.4 A

The supervisory control equipment atthecontrol andremote stations may be of. any suitable type, being,for example,1 substantially similar to that described in. detailin Patent N `2,091,301 which issued on August-31x 41937 to- Han-s P. Bosf wau. Accordingly, the bulk of the supervisory control equipme -t at the controlstation may be represented lby the enclosure 25 while that at the remote station; may be represented by the en- In order to provide for maintaining two-way supervisionM off the signal channel, which comprises in the present instance a telephone line which may be interrupted by means of repeaters,

sending relays 2'0I and! M2A and' a source of direct current', we preferV to use `separate oscillators 2'8 and 2`9\ atthe control and remote stations for operatlng the line relays 10U and" 2'00 at the remote and control stations selectively. For example,` the oscillator 2 may be connected to the telphone line Ill through the hybrid coil I5 for normall'y applying thereto a potential having afrequency 'in the lowerportion of' the audio range, for example, 245 cycl'esfper second.n `The oscillator 28` may be normally energized and connected to the line Ill through the hybrid coil |75, and disposed Vto be keyed for sending` impulse signals by the impulse sending relay 20| through contact members 2li I a, which. turn the oscillator `olf in response to operation of th'eimpulse sending relay. Theline relay ld at the remote station may be made selectively responsive only to the frequency of the oscillator 28- by connecting it to the telephone line through anlter 30 responsive 2 ond. A suitable amplifier 3|, and rectifying means 32 may be provided so as to produce direct-current impulses in response to operation of the oscillator 28. f

The line relay 200 at the control station may likewise be made selectively responsive to the cs cillator 29 of the remote station by connecting it to the telephone line through a filter 34 which is responsive only to the frequency of the oscillator 29, an amplier 35, and rectifier means 36 for providing directcurrent impulses in response to operation of the oscillator 29. The oscillator 29 may be normally energized for applying-to the line a voltage of a different frequency in the lower portion of the audio range, for example, 170 cycles per second. Operation of the oscillator 29 to send coded impulses in response to operation of the impulse sending relay 40| may be eiected by providing for deenergization of the oscillator through contact members lillak of the impulse sending relay.

In order to provide for operating the supervisory control equipment at relatively high speeds, synchronization of the relays at the control and remote stations is essential. Since the line relays at the remote and control stations operate on different frequencies, we have found it desirable to provide for deenergizing the line relay at each station in response to operation of its associated impulse sending relay. This may be accomplished by deenergizing the associated amn plier each time the impulse sending relay operates. Contact members 20|b and 40|b may, therefore, be provided for momentarily shunting the ampliers at the control and remote stations to deenergize the associated line relays each time the impulse sending relays operate. Thus the line relays at each station are subjected in a like manner to the time response characteristics of their amplifiers, rectii'lers, etc., and readily remain in step.

Y In order to prevent interference between the telephone equipment and the supervisory control and line supervision equipment, high-pass lters 38 and 40 may be connected between the microphones and |2 and the oscillators 28 and 29, respectively. The filters 38 and 40 may be used to eliminate from the telephone circuit audio frequencies in the lower portion of the audio range which are not necessary for intelligible speech. For example, they may block all frequencies below about 300 cycles per second, and thus prevent operation of rthe supervisory equipment in response to voice tones. Suitable speech iilters 4| and 42 for blocking frequencies of the same range may be connected between the telephone receivers I3 and I4 and their respective hybrid coils to prevent interference with telephone reception, of the signal and supervisory frequencies.

Since the line relays 200 and 430 are normally energized and are released only for relatively short intervals during impulse signalling, provision may be made for indicating a fault condition of the telephone line whenever the line relays remain deenergized for a time interval greater than that required for signalling. Accordingly, means, such as the time delay relay 44, may be utilized at the control station for completing an energizing circuit for indicating means such as the alarm bell 45 whenever the line relay 200 remains in the deenergized position for'more than a predetermined time.

At the remote station, operation of the apparatus tofbe controlled may be eiected by the supervisory control equipment through the controlled relays 3|9 and 320 of the Boswau patent which may be arranged for respectively energizing and shunting down a control relay l for operating a transmitter or the like in a manner similar to 5 that described therein for closing and opening a circuit breaker. In order to provide adequate protection for the controlled apparatus, which may be a transmitter or the like, the control relay 4l may be provided with a holding circuit through contact members Illa to indirect positive. Accordingly, whenever the line relay 4U() remains deenergized long enough for the release relay 402 of the Boswau patent (not shown) to drop and remove direct positive from the supervisory equipment, the control relay 41 is deenergized and opens contact members llb thereby deenergizingthe transmitter, etc.

In operation, the oscillators 28 and 29 may be normally energized so that the line relays 403 and 233 are normally in the energized position. Accordingly, the relay 44 is normally maintained in the energized position, and the relay 4l is maintained in the energized position so long as the transmitter at the remote station is being over the telephone line I0 independently of the signal and supervision frequencies since these are blocked from the telephone equipment. Operation of the supervisory control equipment may be effected in a manner substantially similar to that described in the Boswau patent hereinbefore referred to, since each time the impulse sending relay 2| at the .control station or 40| at the remote station is operated in sending an impulse signal, its associated line relay 200 or 400 is deenergized by shunting of the amplifier 35 or 3|, respectively, each time the oscillator 28 and 29 is momentarily deenergized to send an impulse signal. Accordingly, impulse signals may be sent in the usual manner for effecting point selection, point check, operation and supervision of the apparatus at the remote station. When the operation code is seni-to set the transmitter at the remote stationinto operation, the operation relay 320 operates and connects the control relay 11 to the source through contact members 320d. A holding circuit isr established through armature 41a. When the operation code is sentto shut the transmitter down the relay 3|9 operates and shunts the control relay at contact members 3 9a,

Each time the line relays 20D and 1D0 are deenergized during impulse signalling, the timedelay relay 44 is also deenergized. Due to its time-delay characteristics, however, this relay remains in theenergized position during any of the periods of deenergization normally encountered during signalling. However, shoulda short circuit, open circuit, or other fault condition occur on the telephone line, particularly during an interval when the transmitter is operating, the voltages received by the ampliers 3U and 35 will be suiciently attenuated to cause deenergization of the line relays so long as the fault condition exists. When such a fault condition exists 65 for a period of time greater than the period of deenergization encountered during signalling, the

line relays drop, and the time-delay relay lill and the control relay 41 return to the deenergized position. Accordingly, an indication of the fault 70 condition is given at the control station by the sounding oi an alarm bell 45. VAt the remote station, the relay 41 effects an indication of 'the fault condition .by opening contact members 41D,

thus deenergizing the apparatus being controlled. 75 Whenever the transmitter is shut downfthe alarm operated. rIelephone conversation may be had d is still operable to `indicate a fault condition since the oscillator 29 is normally energized.

From theabove description and the accompanying drawing, it will be apparent'that we have provided in `-a simple and effective manner `for providing two-way supervision of a signal channel or asupervisory lcontrol system, over a telephone line. Operation of the supervisory control equipment may be effected without interference with operation of the telephone equipment since these -circuits are effectively isolated. Positive -indication is provided for indicating at both ends of theline afault condition on the line, regardless of the location of the fault. Since the same oscillators and receivers'are used for Iboth the supervisory control equipment' and for line supervision, a minimum of apparatus is required and maintenance thereof is'greatly simplied.

Since certain changesmay be made in the above described construction, and different embodiments of the invention may be made without departingfrcm the spirit or scope thereof, it is intended that all the Vmatter contained in the above description and shown in the accompanying drawing shall be considered as illustrative but not in a limiting sense.

We claim as our invention;V

1. In a signal system for two stations connected by a signalling channel, means at one station for supplying to the channel electrical energy of one frequency, means at the other station for supplying to the channel electrical energy of a different frequency, supervisory control equipment at each of the stations including sending means for interrupting the supply of electrical energy to the channel at each station for producing coded impulse signals and receiving means including control means responsive only to the frequency of the other station, and means at each station responsive to deenergization of the control means for greater than a normal impulsing interval for indicating a channel fault condition.

2. The combinationwith a telephone system wherein a telephone line connects a pair of stations provided with telephone equipment, of means for removing from the telephone equipment voice frequencies below a predetermined frequency, means at one station for normally applying to the line electrical energy at a frequency below said predetermined frequency, means at the other station for applying to the line electrical energy at a different frequency .below said predetermined frequency, means including a receiver at each station responsive only to the frequency of the other station and rectifier means for producing direct-current control voltages, supervisory control means at each station including normally energized receiving means responsive to the direct-current voltages and sending means cooperative with the receiving means to interrupt the energization of the line and deenergize the receiving means to produce coded impulse signals, and means at each of the stations responsive to deenergization of the receiving means for a period greater than that of the coded impulse signals for indicating a fault condition.

3. The combination with a telephone system having a telephone line connecting telephone equipment at remotely located stations, of filter means for blocking audio frequencies below 300 cycles from the telephone equipment, sugpervisory control means at each station for controlling from one station apparatus at the other station including impulse sending means and impulse receiving means, means 'at the one station fornormally applying a potential `of oneffequency below 300 cycles `to the telephone 'line and operable under the control of the impulse sending means at said `one station to remove said 5 potential from the line, means at the other station for normally applying a different frequency below 300 cycles to the line and operable under the control of the impulse sending means at said other station to remove said potential `from the line, receiving means at said one station responsive only `to said different frequency for operating the impulse receiving means at said one station, receiving means ati said other station responsive onlyvto said one frequency for operating the impulse receiving means at said `other station, indicating means at said one station responsive to deenergization of the impulse receiving means at said one station for greater than a normal impulsing period for indicating a fault condition of the line, and control means at the other station for insuring deenergization of the apparatus at said other station upon the occurrence of a `fault conditionion the line.

4. The combination in a supervisory control system for a radio transmitter located at a remote station having telephone equipment connected by a telephone line to telephone equipment at a control station, of high-pass filter means connected between the telephone equipment and the line at both stations for blocking frequencies below a predetermined voice frequency in the lower range of the audio range, means at the control station for normally applying to the line a potential of a frequency below said predetermined frequency, means at the remote station for normally applying to the line a potential of another frequency below said predetermined frequency, supervisory control means at each station including an impulse sending relay operable to remove the line potential from said station and impulse receiving means normally operable in response only to the potential from the other station for maintaining an operating potential on the supervisory control means, and means con- 45 trolled by the impulse receiving means for indicating a line fault condition if either line potential is removed for a greater period than normally used in signalling.

5. For use in controlling apparatus at a re- 50 mote station having telephone equipment connected by a hybrid coil to a telephone line extending to a control station wherein it is connected by a hybrid coil to telephone equipment,

a signalling system comprising, high-pass lter means connected between the hybrid coil and the telephone equipment to block audio frequencies in the lower range of voice frequencies, supervisory control equipment at each of the stations including an impulse sending relay and an impulse operated relay for controlling apparatus at the remote station, an audio oscillator at the contro1 station normally applying to the line a potential in one range of frequencies in the lower range of voice frequencies and controllable by the impulse sending relay to send coded impulse signals, means at the remote station including a receiver responsive only to said one range of frequencies for operating the remote station impulse operated relay, means at the remote station operative after the impulse operated relay remains in the deenergized position for a greater time than required for impulse signalling to effect deenergization of the apparatus at the remote station.

6. In a supervisory system for apparatus at a remote station, means at the remote station and a control station for applying potentials of different frequencies to a signalling channel connecting the stations, receiver means at the remoterstation normally operable to receive only the frequency of the control station, supervisory control receiving means at the remote Ystation operated from the receiver, supervisory control sending means at each ofthe stations, each of said sending means controlling the operation of the means at its station to produce coded impulses for operating the receiving means at the other stationand controlling the operation of its associated receiving means to operate said receiving means in step with the receiving Vmeans at the other station, and control means at each ofthe stations` responsive to deenergization of the receiving means for longer than a coded impulse for indicating a fault condition of the signalling channel. 1 Y

t '7. In a supervisory control system for controlling apparatus at a remote stationfrom a control station over a telephone line connecting telephone equipment at thek stations, high-pass fll- -ters connected between the telephone equipment and the line for blocking frequencies below 300 cycles, an oscillator at the control station for normally applying to the line a potential of a frequency below 300 cycles, an oscillator at the remote station for normally applying to the line a potential of a different frequency below 300 cycles, receiving means at each station responsive only to the frequency of the other station for producing a unidirectional potential, supervisoryA control means at each station including an impulse receiving relay operable under the control of its associated receiver and an impulse sending relay operable to key the associated oscillator to send coded impulse signals and to render the associated amplier ineffective simultaneously, and means at theremote station responsive to deenergization of the impulse receiving relay for greater than a normal impulse signal period for effecting deenergization of the apparatus being controlled.

MARTIN G. SATEREN. WILLARD A. DERR. 

